A. Field of the Invention
The present invention relates to a new and improved reflectance instrument; and, more particulary, to a new and improved dual function optical readhead for photometric measurements of diffuse reflectance and/or full-duplex communication with peripheral devices.
B. Description of the Background Art
Whole blood glucose test strips have been used for many years by hospitals, doctors, and individual patients for monitoring glucose levels in patients' blood to determine the stages or status of diabetes and other ailments. The whole blood glucose test strips are used with a reflectance instrument or meter and a work station or other data processing equipment. Tests are conducted using the instrument, and the test results can be stored in a memory in the instrument along with time, date, patient information and operator information. Periodically, the test results are transmitted by a hard wire connection to the work station or the data processing equipment for processing.
Typically, a test is conducted by inserting a reacted test strip into a slot or access port in the instrument. Light from a light emitting diode in the instrument is directed at the reacted test strip. The light is then reflected back to a photodetector also in the instrument, and the reflected light is measured. The instrument includes software that converts the amount of measured reflected light to units of blood glucose by means of an algorithm.
A typical use of the reflectance instrument is for a nurse making his or her rounds in a hospital to test the blood of several patients and store the test data and patient information in the memory of the instrument. Upon the completion of the nurse's rounds, the reflectance instrument is coupled to a work station or other data processing instrument through a hard wire connection such as a cable. The collected test data and patient information are communicated to the work station and processed. Processing can include comparing accumulated data to earlier test data to determine a trend or a long term fluctuation in the glucose levels in the patient's blood. This information can be used to assist the doctors in diagnosis and treatment, and also to assist patients in the control of their disease.
Reflectance instruments typically have size limitations. It is preferred that the instruments be of a size to allow them to be carried easily by a patient. This encourages patients to carry the instrument on his or her person and to test the glucose level of their blood several different times during each day. The test data are maintained in the memory of the instrument, and the patient periodically visits his or her doctor whereupon the reflectance instrument is coupled to a work station or data processing machine in the doctor's office by a hard wire connection and data are transmitted for analysis. The size requirements are also important for nurses since they must carry the instrument through their rounds.
These size requirements make it difficult to incorporate additional circuitry or software in the instrument to accommodate desired features such as data transfer. The size of reflectance instruments could be maintained at a user friendly size if another form of communication or data transfer could be developed that did not require the software and hardware required by the current instruments.
A reflectance instrument can include an LED (light emitting diode) and a photodetector. The instrument operates by applying a drop of blood to a glucose strip. Reagents in the pads of the strip react with the blood resulting in a color corresponding to the glucose level. This strip is then inserted into an access slot or port in the readhead position of the instrument to position the reacted pads adjacent to the LED and the photodetector. The LED is then pulsed to radiate the reacted pads with light. Light reflected from a pad is detected by the photodetector. The photodetector current is converted to percent reflectance by the analog to digital converter and microprocessor circuitry. Percent reflectance is converted to glucose concentration (mg/dL). The glucose reading, date, time, operator, etc. can temporarily be stored in the instrument. These data are transferred via an interface through a cable to a work station where software is used to analyze a chronological data base for each patient. This means of communication and the related structural elements that are required significantly increase the size and cost of the system which includes the reflectance instrument, interface circuitry, connectors, cables, work station and/or data processing equipment.
Less cumbersome ways to communicate or transfer data have been tried in other industries. For example the Hewlett Packard 82240A computer printer can be used to receive data using infrared light.
It would be desirable to provide a way to communicate between a reflectance instrument and data processing equipment while maintaining the compact size of the reflectance instrument and minimizing the overall costs.